Well, to be honest, it depends on the player and his/her team.
Latias and Latios do not have any difference in stats, except that the 110-130 base stat distribution for Sp.A and Sp.D are different. Latios is a more offensive Pokemon, sporting a good base 130 base Sp.A still with good walling and support capabilities with its 110 base Sp.D stat.
Latias is the reverse, being a more defensive Pokemon, with 110 Special Attack and 130 Special Defense, it has very good walling and support capabilities while still maintaining a strong Special Attack stat.
Latios is more suitable for offensive teams used mainly for sweeping while Latias is more suitable for defensive, support or stall teams. The only main weaknesses both of them have is their mediocre HP and Defense stats and also their weakness to five types- Dragon, Ice, Bug, Ghost and Dark.
Other than that, they are awesome Pokemon suitable for Uber and OU Teams :3, although Soul Dew is banned in OU...